Abstract: A data entry device with a resistive layer enables a user to enter data both by finger and stylus. The stylus is electrically connected to the device. An AC driver drives the layer with a time-varying voltage for capacitive finger detection. A DC driver drives the layer with a substantially constant voltage for resistive stylus detection. The AC driver is disabled when the capacitance of the stylus relative to ground is increased due to the user's hand holding the stylus.

Abstract: A graphical tablet includes a pair of parts to be brought into electrical contact with one another under user-interaction. Electrical signals are generated indicative of X and Y coordinates of the contact. The signals are filtered by a low-pass filter. The filtered X and Y signals are sampled with a particular sampling frequency and are held in separate X and Y holding circuits. The cut-off frequency of the filter is at least part of the time substantially lower than the sampling frequency, as each holding circuit has to settle for only increments and decrements relative to its stored sample value. Thus the spectrum of noise rejection is widened with respect to the prior art.

Abstract: A touch screen device includes a panel; a sensor coupled to the panel for detection of a force applied to the panel and a data processor coupled to the sensor for processing data transmitted by the sensor upon detection of the force. The sensor is provided to be co-deformable with the panel for detecting a deformation of the panel itself as a result of the force being applied. This avoids the use of a rigid frame as in conventional devices, saving weight, costs and components, and reducing manufacturing problems. The sensor means may comprise strain gauges that are physically integrated with the panel. Combined with a display such device presents a minimum parallax.